This invention relates to new gas separation membranes fabricated from polymers containing a hydrocarbon backbone and pendant metal ionomer groups. The invention further relates to a method of separating gases using the membranes herein disclosed.
The use of membranes to separate gases is well known in the art. Hydrogen, helium, oxygen, nitrogen, carbon dioxide, methane, and light hydrocarbons are some of the gases which have been separated by membrane processes. Particular applications of interest include obtaining an enriched oxygen stream from air. The enriched oxygen may be used for enhancing combustion or increasing the efficiency of biological fermentation or cell culture processes. Another desirable application is the production of an enriched nitrogen stream from air, which may be used for inert padding of flammable fluids in transit or storage. An enriched nitrogen stream may also be used to increase food storage time. Gas separation by membranes has also been useful in hydrogen recovery and in the separation of carbon dioxide and light hydrocarbons as part of the tertiary oil recovery process.
To separate a gas mixture, the gaseous components are contacted with one side of a semipermeable membrane through which at least one of the gaseous components selectively permeates. A gaseous component which selectively permeates through the membrane passes through the membrane more rapidly than the other component(s) of the mixture. The gas mixture is thereby separated into a portion which is enriched in the selectively permeating component(s) and a portion which is depleted in the selectively permeating component(s). A portion which is depleted in the selectively permeating component(s) is enriched in the nonpermeating component(s). A non-permeating component permeates more slowly through the membrane than the other component(s). The membrane material is chosen so that some degree of separation of the gaseous mixture can be obtained.
Membranes have been fabricated from a wide variety of polymeric materials. An ideal gas separation membrane possesses a high separation factor, high gas permeability, and good mechanical properties. Polymers possessing high selectivities generally have undesirably low permeabilities. Those polymers having high permeabilities generally have low separation factors. In the past, a choice between a high gas permeability and a high separation factor has been required. There is a need to develop a membrane which overcomes the necessity of choosing between a high selectivity and a high gas permeability.